1. Field of the Invention
The present invention is related to a cooling fan having dual blade sets, and more particularly to a cooling fan that is able to draw out heat generated by the cooling fan itself.
2. Description of Related Art
Cooling fans are commonly used inside electronic devices and appliances for heat dissipation. The cooling fans are embedded in the host machines, such as computers and image projectors, to create an internal air flow in the inner space of the host machine, so that the internal heat can be quickly driven out during the operation of the host machine.
However, the stator and rotor of the fan motor themselves produce heat in order as they make the impeller turn. According to the conventional design of the cooling fans, the heat is usually trapped in the enclosed space between the impeller and the shell, which causes the temperature inside the cooling fan to rise continuously as long as the cooling fan is running. The rising temperature and built-up thermal pressure in the impeller will eventually cause thermal breakdown of the fan motor. Therefore, this is a problem which may shorten the normal service life of a cooling fan if not properly controlled.